The present invention relates to a technique for setting up an optical disc apparatus.
JP-A-2004-273000 can be cited as one example of the prior art pertinent to the present technical field.
JP-A-2004-273000 sets forth an optical disk device providing focus control for bringing an optical head 2 in a position on each recording/reproducing layer on the basis on both a focus error signal created from laser light reflected from the recording/reproducing layers formed on one side of an optical disc 1 and on a focus summation signal, the device being characterized in that it achieves a servo stability comparable to that for adjusted recording/reproducing layers even when moving to any unadjusted recording/reproducing layer by obtaining an amplitude of the focus error signal regarding the reflectance from each layer and setting a coefficient having an inverse relationship to the amplitude to a normalizing gain prepared for each layer, thereby the result of adjustment of a closed servo loop used for focusing and adjusted for one layer can also be applied to a different layer having an unadjusted recording/reproducing layer.